Tank help

Look like it froze and split open, in Texas yet???

Sounds like a hot water storage tank. It would make a larger amount of hot water.
I've never seen something like that.

Dusty

It has an upper and a lower hose and is directly connected to the hot water heater, it's a poor photo due to the tank being located in an unreachable area but I'll post more photos today when I remove it.

If it has only one entry/exit connection it is a pressure accumulator tank. Your picture only shows one.

A hot water tank will have an upper and a lower entry/exit hole. The hot water tank will also be located on an outside panel and have a removable outside screen.

If the tank is round as it looks, it's a pressure accumulator tank. Likely it held water in the lower half and did not drain when frozen, then it froze and broke open.

It did have insulation and i do believe it's the water heater tank. The tank I thought was the gray water is in fact the fresh water. So I think I have a bit of a job on my hands

Are you sure it's hooked to the gray water tank? That makes little sense to me. If indeed it is, then it may be a housing or storage tank for some sort of a filter system (quite possibly a reverse osmosis system with the gray water drain) and it's hard to suggest what to use for repair or replacement without a little more information.

If it's next to the water pump, it may be a pressure accumulator tank. A replacement would have to likewise be a pressure accumulator tank, but it could be a different style or construction. There are some for RV use that are plastic. (If that's what it is, it could also be bypassed safely, though the water flow is not as constant and the pump cycles more frequently without it.)

If perchance it's the water heater tank, it would not have a gray water connection, and it should not be replaced with a plastic tank. I don't think I've seen an RV water heater tank that looks like that, and in particular that is uninsulated, but there are many things I haven't seen.